Rocks? That could be a short form for 'rockets.' Perhaps a translation error. ;>
Or perhaps those 'Little Boys' and 'Fat Man's' look like rocks from a distance.
Either way, whatever works. I tend to believe that God works through his people these days. He has provided us with the means to do his will.
1 - yes, I would agree it will be justice. Eze 36-37-38-39 - facinating story.
2 - As for a translation error about "rocks" .. remember - the people who wrote this had never seen a rocket. And .. don't discount hail as being rocks.
3 - Yes, GOD does work through his people but this fight will be against the foes of Israel - and GOD has a separate covenant with them.